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/*******************************************************************************
*
* McStas, neutron ray-tracing package
* Copyright 1997-2008, All rights reserved
* Risoe National Laboratory, Roskilde, Denmark
* Institut Laue Langevin, Grenoble, France
*
* Component: Mirror_Parabolic
*
* %I
* Written by: <a href="mailto:desert@drecam.cea.fr">Sylvain Desert</a>
* Date: 2007
* Origin: <a href="http://www-llb.cea.fr/">LLB</a>
* Modified by: E. Farhi, uniformize parameter names (Jul 2008)
*
* Parabolic mirror.
*
* %D
* Models a parabolic mirror. The reflectivity profile is given by a 2-column reflectivity free
* text file with format [q(Angs-1) R(0-1)].
*
* Example: Mirror_Parabolic(reflect="supermirror_m3.rfl", xwidth = 0.05, xshift=0.05,
* yheight = 2e-4, focus = 6.6e-4)
*
*
* %P
* INPUT PARAMETERS:
* xwidth: [m] width of the illuminated parabola
* xshift: [m] distance between the beam centre and the symetric axis of the parabolla
* yheight: [m] height of the mirror
* focus: [m] focal length
* reflect: [q(Angs-1) R(0-1)] (str) Reflectivity file name. Format
* R0: [1] Low-angle reflectivity
* Qc: [AA-1] Critical scattering vector
* alpha: [AA] Slope of reflectivity
* m: [1] m-value of material. Zero means completely absorbing.
* W: [AA-1] Width of supermirror cut-off
*
* Example instrumentfile FocalisationMirrors.instr is available in the examples/ folder.
*
* %E
*******************************************************************************/
DEFINE COMPONENT Mirror_Parabolic
SETTING PARAMETERS (string reflect=0, xwidth=0.05, xshift=0.019, yheight=2e-4, focus=6.6e-4,
R0=0.99, Qc=0.0219, alpha=6.07, m=1.0, W=0.003)
/* Neutron parameters: (x,y,z,vx,vy,vz,t,sx,sy,sz,p) */
SHARE
%{
%include "read_table-lib"
%include "ref-lib"
%}
DECLARE
%{
double beta1; /* parabola half-axis */
double gamma1;
t_Table pTable;
int err; /* counts neutron absorbed for anormal reasons */
int nom;
int vz_neg;
%}
INITIALIZE
%{
double alpha1; /* width of the parabola */
if (reflect && strlen(reflect) && strcmp(reflect, "NULL") && strcmp(reflect,"0")) {
if (Table_Read(&pTable, reflect, 1) <= 0) /* read 1st block data from file into pTable */
exit(fprintf(stderr,"Mirror_Parabolic: %s: can not read file %s\n", NAME_CURRENT_COMP, reflect));
}
alpha1 = xwidth+xshift;
gamma1 = -1/(4*focus);
beta1 = -gamma1*alpha1*alpha1;
err = 0;
nom = 0; /* number of reflections on the mirror */
vz_neg = 0;
yheight/=2;
%}
TRACE
%{
double angle;
double q, B;
double div,z1,x1,z2,x2;
double v;
double vx_2,vz_2;
int i=-1;
double oa,ob,ab,xa,za;
double a, b; /* parameters for neutron propagation */
double old_x,old_y,old_z;
double delta; /* angle: angle between themirror and z-axis */
double par[5] = {R0, Qc, alpha, m, W};
/* First check if neutron has the right direction. */
if((vz != 0.0 && -z/vz >= 0) && x-xwidth-xshift < 0)
{
do{
i++;
old_z=z;
old_x=x;
old_y=y;
a=vz/vx;
b=z-a*x;
/*calculation of intersection with the parabola*/
delta = sqrt(4*gamma1*(b-beta1)+a*a);
x1 = (a - delta)/(2*gamma1);
x2 = (a + delta)/(2*gamma1);
z1 = gamma1*x1*x1+beta1;
z2 = gamma1*x2*x2+beta1;
/*choose the correct answer*/
if(z1>z2){
z=z1;
x=x1;
}
else{
z=z2;
x=x2;
}
/* absorbs the neutron if the difference between the 2 calculation methods is larger than 1% */
if(fabs(z-a*x-b)>0.01){
#pragma acc atomic
err = err +1;
ABSORB;
}
/* calculation of y*/
y+=vy*(z-old_z)/vz;
/*reflection*/
if((x-xshift)>0 && fabs(y)<=yheight){
#pragma acc atomic
nom = nom + 1;
/* reflection angle in the xz plane */
div = -atan(vx/vz);
angle = atan(1/(2*gamma1*x));
/* vx and vz calculation after reflection */
v=sqrt(vx*vx+vz*vz);
vz = v*cos(2*angle+div);
vx = v*sin(2*angle+div);
/*incidence angle in 3D*/
ob = sqrt((old_x-x)*(old_x-x)+(old_z-z)*(old_z-z));
ab = ob*cos(-div+angle);
/* printf("%e = %e * cos(%e)",ab,ob,div+angle); */
xa = x+ab*sin(-angle);
za = z+ab*cos(-angle);
oa = sqrt((old_x-xa)*(old_x-xa)+(old_z-za)*(old_z-za));
ob = sqrt((old_x-x)*(old_x-x)+(old_y-y)*(old_y-y)+(old_z-z)*(old_z-z));
/* printf("\nob : %e / ab : %e\nO: %e / %f / %f\nA : %e / %f / %f\nB : %e / %f / %f\nAngle : %e rad / Div : %e rad\n",ob,ab,old_x,old_y,old_z,xa,old_y,za,x,y,z,angle,div); */
ab = sqrt((xa-x)*(xa-x)+(old_y-y)*(old_y-y)+(za-z)*(za-z));
angle = acos((-ab*ab-ob*ob+oa*oa)/(2*ab*ob));
v=sqrt(vx*vx+vy*vy+vz*vz);
q = fabs(2*sin(angle)*v*V2Q);
/* Reflectivity (see component Guide). */
if (reflect && strlen(reflect) && strcmp(reflect, "NULL") && strcmp(reflect,"0"))
TableReflecFunc(q, &pTable, &B);
else {
StdReflecFunc(q, par, &B);
}
if (B <= 0) { ABSORB; }
else p *= B;
}
if(vz<0){
#pragma acc atomic
vz_neg = vz_neg + 1;
ABSORB;
}
}while((x-xshift)>0 && fabs(y)<=yheight);
if (i<0) fprintf(stderr,"Mirror_Parabolic: %s: out mirror\n", NAME_CURRENT_COMP);
y=old_y;
x=old_x;
z=old_z;
SCATTER;
}
else{
ABSORB;
}
%}
FINALLY
%{
/* printf("\n %d neutrons were reflected on the component %s.\n",nom,NAME_CURRENT_COMP);*/
if(err!=0||vz_neg!=0){
fprintf(stderr,"Mirror_Parabolic: %s: %d lost neutrons for inadapted divergence\n"
"\t%d for vz <0 \n neutrons absorbed inside the component.\n",
NAME_CURRENT_COMP,err,vz_neg);
}
%}
MCDISPLAY
%{
double delta0,xi,xf,zi,zf;
delta0 = xwidth/99;
xi = xwidth+xshift;
line (xi,-yheight,0, xi,yheight,0);
do
{
xf = xi - delta0;
zi = gamma1*xi*xi+beta1;
zf = gamma1*xf*xf+beta1;
line (xi,yheight,zi, xf,yheight,zf);
line (xi,-yheight,zi, xf,-yheight,zf);
line (xf,yheight,zf, xf,-yheight,zf);
xi = xf;
}while(xf>=xshift);
%}
END
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